1. Field of the Invention
The present invention relates generally to treating sanitary wastewater and, more particularly, the purification of solids-free wastewater utilizing submerged fixed film biological technology and bioreactors.
2. Discussion of the Background Art
In areas of the country where municipal or publicly owned treatment systems do not provide service for the disposal of sanitary wastes, sanitary wastewater from residential, commercial and industrial sites is treated on-site in privately owned treatment systems and either disposed of, reused on-site or discharged under a permit regulated by the National Pollutant Discharge Elimination System (NPDES) and/or anti-degradation regulations. In areas where an NPDES discharge is possible, discharge may not be permitted since many package sanitary treatment plants cannot consistently achieve the requisite discharge standards. This is partially true if the discharge is to a designated National, State, Scenic or otherwise protected surface water body, which requires compliance with anti-degradation regulations. The purpose of the National Pollutant Discharge Elimination System (NPDES) Program is to protect human, health and the environment. The Clean Water Act requires that all point sources discharging pollutants into waters of the United States must obtain an NPDES permit. United States EPA definition of point sources includes means discrete conveyances such as pipes or man made ditches. Although individual residential treatment systems do not require permits, larger facilities must obtain permits if they discharge directly to surface waters.
As a consequence, the inability to treat and discharge sanitary waste in an acceptable and/or cost effective manner greatly restricts residential, commercial and industrial development. Residential, commercial and industrial development is restricted in areas where low permeability soils prohibit or restrict wastewater discharge to leach fields, evaporative and transpiration fields or mound systems. Ground saturation and the leakage of these systems results in a non-point source discharge of poorly treated contaminated liquids to surrounding surface water bodies (e.g., lakes, rivers, streams). Sanitary wastewater discharged from agricultural sites such as cattle, pig, and poultry concentrated feed operations (feed lots), require greater degrees of treatment due to existing, proposed, and anticipated regulatory standards to prevent contamination of surface water bodies.
In some areas, solids-free sanitary wastewater is treated using constructed wetlands. However, due to the temperature sensitive nature of the micro-organisms involved in the sanitary waste degradation process, constructed wetlands can have poor waste treatment efficiencies in geographic regions that experience cold temperature periods. Due to more stringent regulatory discharge requirements and an ever increasing population, public sanitary treatment facilities continually are forced to expand and upgrade to improve water quality and increase discharge capacity. However, due to increasing regulatory requirements, in particular anti-degradation requirements, an increase in discharge capacity requires corresponding decrease in pollutant concentration so that the mass loading of contaminants to the water body remains the same, despite increasing the flow volume.
Historically, the treatment of sanitary wastewater has employed aerobic and, to a lesser extent, anaerobic biological treatment technology utilizing micro-organisms in a suspended growth or, to a lesser extent, fixed film aqueous environment. Unfortunately, the control of environmental factors such as temperature, pressure, and airflow for existing systems is rather haphazard and significant variation in treatment efficiencies can occur.
There is a great need to provide improved methods and systems for treating sanitary wastewater so that the effluent can comply with existing and increasingly restrictive future water quality standards. There is a need to mitigate effluent discharge restrictions currently imposed on existing wastewater treatment technologies and allow residential, commercial and industrial development in areas where access to sanitary municipal/publicly owned treatment systems (sewers) are not available and/or in areas where low permeability soils exist and preclude on-site discharge of treated sanitary wastewater produced by current technology. There is a great need to provide improved methods and systems for treating wastewater discharge from agricultural facilities.
There is a great need to provide improved methods and systems for treating wastewater in place of constructed wetlands or, alternatively, in combination with constructed wetlands to substantially improve the effluent water quality from the constructed wetland, which is either discharged and/or allowed to percolate into the ground. There is also a need to provide improved methods and systems for treating wastewater from municipal wastewater treatment facilities, which are often publicly owned, due to more stringent regulatory discharge requirements and an ever increasing population. Public sanitary treatment facilities, such as municipal wastewater treatment facilities, are continually upgrading to achieve better water quality and increase discharge capacity. Due to increasing regulatory requirements, in particular anti-degradation requirements, an increase in discharge capacity requires corresponding decrease in pollutant concentration so that the mass loading of contaminants to the water body remains the same despite increasing the flow volume. Therefore, a need exists for a tertiary polishing of municipal sanitary wastewater to achieve higher levels of wastewater treatment efficiency, thereby, increasing the potential capacity of the municipal wastewater treatment system.
An exemplary embodiment of the invention includes a wastewater treatment plant having, in serial fluid flow relationship, a wastewater source, a wastewater treatment plant, and a discharge site. The wastewater treatment plant has, in serial fluid flow relationship, an aerobic bioreactor in fluid flow communication with the wastewater source and an anoxic bioreactor in fluid flow communication with the discharge site.
Fixed film packing for growing microbes is disposed in first and second tanks of the first and second bioreactors, respectively. A primary holding tank is disposed between the wastewater source and the aerobic bioreactor. A first pumping means is used for pumping liquid out of the primary hold tank through a first pressure line leading into the first tank through a pressure line outlet in a bottom of the first tank. One embodiment of the first pumping means is a float activated primary hold tank pump which is activated by a normal level float switch. Some embodiments of the invention have a septic tank between a solids laden wastewater source and the primary holding tank.
The liquid in the first tank is flowed out through a first tank outlet near a top of the first tank, through a transfer pipe in fluid communication with the first tank outlet, and into a bottom of the second tank through a transfer pipe outlet at the bottom of the second tank. An air supply means, such as a blower, is used to supply air to the bottoms of the first and second tanks. The liquid in the second tank is flowed out through a second tank outlet near a top of the second tank, through an exit pipe in fluid communication with the second tank outlet and into a secondary holding tank, which is in fluid communication with the discharge site.
A bioreactor building encloses the aerobic and anoxic bioreactors and a heater or some other heating device is suitably located in the building and operable to control temperature inside of the building. At least one blower is connected in fluid communication with air lines that lead to air distribution manifolds near the bottoms of the first and second tanks. The air distribution manifolds have air outlets.
A first fluid distribution manifold is connected to the first pressure line near the bottom of the first tank and a second fluid distribution manifold is connected to the transfer pipe near the bottom of the second tank. The fluid distribution manifolds have downwardly facing fluid flow openings that discharge fluid downwardly towards the bottom of the tanks. The manifolds are constructed from straight pipes connected by T fittings. The T fittings have downwardly facing collars and bushings that fit and are received inside of the collars and include the fluid flow openings to discharge the fluid downwardly towards the bottom of the tanks. The fluid flow openings in the bushings are used to help regulate the fluid flow through the fluid distribution manifolds.
In one embodiment, the bushings in each of the fluid distribution manifolds have graduated size fluid flow openings radially across the fluid distribution manifold which increase in size in a direction going away from a manifold inlet of each of the fluid distribution manifolds. The air outlets are graduated in size and increase in size in a direction going away from the air lines.
Vent pipes are located at the tops of the tanks and are connected to a vent manifold, which in turn is vented to an exhaust pipe extending outside of the bioreactor building. A vent air control valve is operably installed in the vent manifold. A controller operably connected to the valves and heater in the bioreactor building is programmed to control temperature inside of the building and the bioreactors and to control process of the plant. The controller is programmed to maintain a first temperature in the first bioreactor between 45/F. and 120/F. and a second temperature in the second bioreactor between 55/F. and 120/F. The controller is further programmed to maintain airflow from the blower through first bioreactor between 0.034 to 0.067 cubic feet of air per minute (cfm) per cubic foot of packing in the first bioreactor and through the second bioreactor between 0.013 to 0.027 cfm of air per cubic foot of the packing in the second bioreactor. The controller is further programmed to provide a wastewater resident time in each of the bioreactors in a range of between 12 and 24 hours.